Add timezone to period value types

The time zone was missing from PERIOD values.
See niccokunzmann/python-recurring-ical-events#113

CHANGES.rst

@@ -18,7 +18,7 @@ New features:
 
 Bug fixes:
 
-- ...
+- PERIOD values now set the timezone of their start and end. #556
 
 5.0.8 (2023-09-18)
 ------------------

src/icalendar/prop.py

@@ -331,7 +331,7 @@ def from_ical(cls, ical, timezone=None):
         if u.startswith(('P', '-P', '+P')):
             return vDuration.from_ical(ical)
         if '/' in u:
-            return vPeriod.from_ical(ical)
+            return vPeriod.from_ical(ical, timezone=timezone)
 
         if len(ical) in (15, 16):
             return vDatetime.from_ical(ical, timezone=timezone)
@@ -548,11 +548,11 @@ def to_ical(self):
                 + vDatetime(self.end).to_ical())
 
     @staticmethod
-    def from_ical(ical):
+    def from_ical(ical, timezone=None):
         try:
             start, end_or_duration = ical.split('/')
-            start = vDDDTypes.from_ical(start)
-            end_or_duration = vDDDTypes.from_ical(end_or_duration)
+            start = vDDDTypes.from_ical(start, timezone=timezone)
+            end_or_duration = vDDDTypes.from_ical(end_or_duration, timezone=timezone)
             return (start, end_or_duration)
         except Exception:
             raise ValueError(f'Expected period format, got: {ical}')

src/icalendar/tests/calendars/period_with_timezone.ics

@@ -0,0 +1,32 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+X-WR-CALNAME;VALUE=TEXT:Test RDATE
+BEGIN:VTIMEZONE
+TZID:America/Vancouver
+BEGIN:STANDARD
+DTSTART:20221106T020000
+TZOFFSETFROM:-0700
+TZOFFSETTO:-0800
+RDATE:20231105T020000
+TZNAME:PST
+END:STANDARD
+BEGIN:DAYLIGHT
+DTSTART:20230312T020000
+TZOFFSETFROM:-0800
+TZOFFSETTO:-0700
+RDATE:20240310T020000
+TZNAME:PDT
+END:DAYLIGHT
+END:VTIMEZONE
+BEGIN:VEVENT
+UID:1
+DESCRIPTION:Test RDATE
+DTSTART;TZID=America/Vancouver:20230920T120000
+DTEND;TZID=America/Vancouver:20230920T140000
+EXDATE;TZID=America/Vancouver:20231220T120000
+RDATE;VALUE=PERIOD;TZID=America/Vancouver:20231213T120000/20231213T150000
+RRULE:FREQ=MONTHLY;COUNT=9;INTERVAL=1;BYDAY=+3WE;BYMONTH=1,2,3,4,5,9,10,11,
+ 12;WKST=MO
+SUMMARY:Test RDATE
+END:VEVENT
+END:VCALENDAR

src/icalendar/tests/test_period.py

@@ -7,6 +7,7 @@
 import pytest
 import pytz
 from icalendar.prop import vDDDTypes
+import datetime
 
 
 @pytest.mark.parametrize("calname,tzname,index,period_string", [
@@ -31,7 +32,7 @@ def test_issue_156_period_list_in_rdate(calendars, calname, tzname, index, perio
     calendar = calendars[calname]
     rdate = calendar.walk("vevent")[0]["rdate"]
     period = rdate.dts[index]
-    assert period.dt == vDDDTypes.from_ical(period_string, timezone=pytz.timezone(tzname))
+    assert period.dt == vDDDTypes.from_ical(period_string, timezone=tzname)
 
 
 def test_duration_properly_parsed(events):
@@ -46,3 +47,17 @@ def test_duration_properly_parsed(events):
     assert period[1].days == 0
     assert period[1].seconds == (5 * 60 + 30) * 60
     assert period[1] == duration
+
+
+def test_tzid_is_part_of_the_parameters(calendars):
+    """The TZID should be mentioned in the parameters."""
+    event = list(calendars.period_with_timezone.walk("VEVENT"))[0]
+    assert event["RDATE"].params["TZID"] == "America/Vancouver"
+
+
+def test_tzid_is_part_of_the_period_values(calendars):
+    """The TZID should be set in the datetime."""
+    event = list(calendars.period_with_timezone.walk("VEVENT"))[0]
+    start, end = event["RDATE"].dts[0].dt
+    assert start == pytz.timezone("America/Vancouver").localize(datetime.datetime(2023, 12, 13, 12))
+    assert end == pytz.timezone("America/Vancouver").localize(datetime.datetime(2023, 12, 13, 15))